The present invention will be described with particular reference to the measurement of cattle. However, it will be appreciated that the system and method of the present invention is applicable to measuring other types of ungulates and no limitation is intended thereby. Examples of animals that may be measured according to the method and system of the present invention include cattle, goats, sheep, giraffes, American Bison, European bison, yaks, water buffalo, deer, camels, alpacas, llamas, wildebeest, antelope, pronghorn, pigs and horses.
It is often desirable to obtain an estimate of an animal's physical size. For commercial meat producing animals, size may be used to monitor growth rate and predict a finishing weight. For non-meat producing animals, it may also be desirable to monitor size and/or growth rate to assist in animal management. In particular, it is also desirable to measure the skeletal growth rate of dairy heifers. Dairy heifers are measured along with weighing to insure heifers do not deposit fat in the udder. When fat is deposited in the udder, their lifetime milk production is lowered dramatically. Traditionally, weight has been used as an approximate measure of size as the measuring equipment is relatively simple.
Meat producing animals are often slaughtered at a target weight. However, animal weight provides little or no information as to the quantity of muscle protein, and total body fat, carcass quality or grade of the meat which is assessed according to the quantity of intramuscular fat or marbling. Expression of intra-muscular fat traits requires that the animal has the genetic capacity for deposition, has not encountered major nutrient intake limitations during its growth period and deposits a critical percentage of total body fat. It is known that intramuscular fat deposition is enhanced as carcass fat increases to a certain level. Thus, an animal that is slaughtered at an optimal body fat content may be more valuable than an animal having lower total body fat and less marbling for a specific market. However, animal weight alone provides little or no information of muscle protein, total body fat or carcass quality.
A factor that is often used to describe the growth potential of cattle is frame score. If an animal's age is known, the relationship between age and the measured hip height can be converted to a frame score. Generally, an animal maintains a constant frame score throughout its life if allowed to consume adequate quantities of nutrients for potential growth. Animals with a higher frame score will have a greater mature body weight than an animal with a smaller frame score when animals are at similar percentage of total body fat.
Knowledge of an animal's frame score together with weight can provide a much more reliable indicator of growth and eventual carcass weight, tissue composition or quality. Still further, measuring both size and weight can provide information regarding the relative amounts of muscle protein and fat deposition. For example, observing animals of similar weight, a large frame score animal will have less total body fat or more muscle protein where a smaller frame score animal has higher total body fat and less muscle protein. Thus, having knowledge of frame score and weight can permit an estimate of total body fat and muscle protein. It will be appreciated that such information is particularly useful for assessing and/or predicting a meat producing animals' finishing weight for slaughter.
Hip height is traditionally measured with a calibrated pole with a slide. In use the pole is placed adjacent the animal and the slide is moved along such that it rests on the animals' back. Making manual measurements of an animal in this manner is time consuming, and in some cases potentially dangerous for the operator. In order to address this problem, an automated method of measuring the pelvic height of an animal using ultrasound has been developed by the present inventor and described in WO99/67631.
In practise however, the age of an animal is not always known which means that the frame score/weight relationship cannot be used to predict body composition. This may be addressed by making measurements at time intervals to determine an animal's growth rate. A fast skeletal and muscle growing animal will deposit little fat, whereas a slow skeletal and muscle growing animal will deposit greater quantities of fat provided access to similar nutritional inputs. Further information regarding the potential of an animal may be obtained by making measurements in addition to hip height. In particular, animal width and length can provide valuable information.
The present inventor has also developed a system and method for measuring skeletal length that utilizes the relationship between the position of an individual bovine legs and skeletal length. Generally, the mid-point between the front legs is substantially perpendicular to the immediate region within or posterior to the point of shoulders of the animal. The mid-point between the hind legs of an animal is substantially perpendicular to the hip joints of the pelvic region of the animal. The system uses a light source and an optical device to obtain a silhouette image of the legs. The image is then processed to determine the position of the animal's legs and obtain an estimate of the skeletal length of the animal. Despite the improvements of this system over prior art methods the present inventor has now developed an alternative method and system for measuring an animal.